Method of making bifocal lenses



H. A. SCHE UERLE.

' METHOD OF MAKING BIFOCAL LENSES.

APPLICATION FILED MAR. 18, I914.

Patented July 5, 1921.

2 SHEETS-SHEET I yVlTNES QLMW/ lNVENTOR: j yv z a n, H. A. SCHEUERLE. fMETHOD OF MAKING BIFOCAL LENSES.

APPLICATION FILED MAR-I3. 1914. V Patented July 5, 1921.

2 SHEETSSHEET 2 INVENTQR? (Ll/3% Ml 1 WITNESSES:

with the axis of rotation of t e UNITED sures PATENT, OFFICE.;

EXECUTRIX OF SAID HENRY A. SCEEUERLE,

DECEASED.

METHOD OF MAKBTG IBH'OOAL LENSES.

To all whom it may concern:

Be it known that I, HENRY A. SoHEUEnm, a citizen of the United States,residing at Philadelphia, in the State of Pennsylvania, have invented acertain new and useful Imrovement in Methods .of Making Bifocal enses,whereof the followin is a specification, reference being had to t eaccompanyin drawing.

y invention relates to a method of abrading one side of glass to formmajor areas for distant vision and minor areas for near vision,regardless of the opposite side thereof, which may be shaped by anyconvenient method or means.

In 'ordina methods of producing such major and mmor areas, the axis ofrotation of the glass and the axis of rotation of the abrading elementhave a relative movement, during the abrading operation, whichisoscillatory, gyratory, planetary or the resultant of freedom for oneor more such movements; the purpose and effect of such freedom being topermit the abrading means to follow the initial curvature of the glassblank so as to minimize the extent of the abradin operation with respectthereto; but suc freedom permits the abrading 'means to followinaccuraciesin the glass banks instead of eliminating them..

In accordancewith my method, the laps positively determine the-finalcurvature of all of the lens areas, by the maintenance of their axes ofrotation in unvaryin relafion ass, throughout each abrading operation.lass for two such lenses, to have respective minor areas adjoining eachother and between their respective major areas, is circularly abraded atthe same time and by the same lap, while rotating with said minor areashaving a, common center of curvature upon the axis of rotation of theglass, and said major areas havin a common center of curvature upon saiaxis. However, said major areas are not abraded at the same time as saidminor areas. Therefore, the major and minor areas maynbe respectivelyreduced to any desired thic ess, and either recessed with respect to theother, or left of the same thickness at a sharply defined junction linebetween said after described. I employ a lap having an annular convexareas, as herein- Speciflcatlon of Letters Patent. Application filed mon18, 1914. Serial no. 825,004.

abradmg surface, for operating upon the ma or areas for two lensessimultaneously, havlng a central recess encircling areas for bothlenses, sion thereof during ma'pr areas. sa i with a stationa axis,(with such axial advance toward t e glass as to abrade the latter,) saidaxls of rotation of the lap is at an angle to the axis of rotation-ofthe glass, an bothof said axes extend through the center of curvature ofsaid major areas, so that the rotation of the lap is eccentric to therotation of the lens and finally, due to the spherical contour of thelap, a spherso as to prevent abra- Although the movement of PatentedJul}' 5, 1921."

the minor the abrasion of the lap is limited to rotation concentricareas, without concentric rotation of the glass and abrading elements,and consequently wlthout the production of any circular ruts orscratches in the lass, althou h the glass is circularly abrade andthroug out a spherical zone concentric with the axis of rotation of theglass. I use the terms circularly abrading and circularly abraded todistinguish the operation of my invention from the aforesaidoscillatory, gyratory and planetary abrading operations characteristicof the prior art.

Although, as herelnafter described, the lens blank or blanks and theabrading means are'relativel rotated u on a common axis during the arasion of t e minor lens areas; which axis extends through centersofcurvature of all of the lens areas, both major and minor; theessential ste in the method of my invention consists in circularlyabrading the major area of what is ultimately a plurality of lenses,while preventing abrasion of the minor area of what is ultimately saidplurality of lenses; the lens blank or blanks and the abrading meansbeing relatively rotated upon axes respectively coinciding withdifferent radii of curvature, but both common to all of the ma'or lensareas.

Mechanism for e ecting such circular abrading operations as abovedescribed, forms the subject matter of Letters Patent of the UnitedStates No. 1,140,401 granted pursuant to application Serial 832,439filed.

The invention herein claimed includes the various novel features ofprocedure hereinafter more definitely specified.

In-the drawing: Figure I is a fragmentary sectional view of a relativelyrotary lensblank holder and lap of the general character abovecontemplated.

Fig. II is a plan view of certain of the elements shown in Fig. I,showing their relatively eccentric relation.

Fig. III s a vertical sectional view of a rotary lap, carrying means forvariously limiting the abradin action thereof, illustrating the method 0adjusting such limit ing means with respect to a templet.

Fig-IV is a fragmentary sectional view of the lap and limiting meansshown in Fig. III, illustrating the method of adjusting such limitingmeans with respect to a lens.

Fig. V is a plan view .of a single blank, adapted to be severed to formtwo oppositely counter art bifocal lenses.

' Fig. I is a longitudinal sectional View of the lens blank shown inFig. V.

Fig. VII is a plan view illustrating the method of abrading the minorlens areas by relative rotation of the abrading tool and lens blanksupon axes respectively coinciding with different radii of curvature, butcommon to all, of the minor lens areas.

Fig. VIII is a sectional view of the abrading tool shown in Fig. VII.

Fig. IX is a front elevation of a convenient form of mechanism foreffecting relative rotation of the lens blank holder and laps invariable angular relation, as indicated in Fig. I, but set with the axesof rotation in alinement.

Fig-X is a side elevation .of the mechanism shown in Fig. IX.

In said figures; the glass which is ultimately to form two similarbifocal lenses may be a single blank 1, as shown in Fig. IV, which whenthe abrasion thereof is completed is divided on the line 2-2 to form twooppositely counterpart bifocal lenses each having a minor area 3 and amajor area 4, or, the lass which is ultimately to form the two bi ocallenses may be primarily separate blanks 6, 6 disposed in oppositelycounterpart relation as shown in Fig. VII. In either case, the axiallyopposite surfaces of the blank 1, or blanks 6, 6, are, initially,spherical surfaces throughout their extent, having a common center ofcurvature. Moreover, the respective minor areas have a common center ofcurvature, on the line 32 which is the radial axis of rotation of saidblank or blanks, and the major areas also have a common center ofcurvature on said radial axis; 'so that said line 32 shown in Fig. I,which is the axis of rotation of the holder 31, extends through centersof curvature of all of the lens areas, both major and minor, throughoutthe abrading operation messes herein contemplated. Saidabradingoperation includes what is termed rough grlndmg,

fine grinding, extra fine grinding, and polishingall of said major andminor areas, and such abrasion is preferably performed in the followingorder, although I do not wish to limit my invention to such order ofoperation, to wit; with the glass and abrading elements relativelyrotating concentriof curvature of said areas 4, saidv areas are extrafine ground and then polished. Then, with said glass and abradingelements relatively rotating, upon relatively eccentric axes, said minorareas 3 are extra fine ground, and then polished. That is to say;

prefer to complete the surfacing operation upon the major areas beforecompleting the surfacing operation upon the minor areas, when the latterare of the greater radius, as in the type lenses I have illustrated. Thereason for that preference is that less care and skill are required toleave the areas of the same thickness at their junctions, (indicated bythe dotted lines shown respectively in Figs. V and VII) than if thesurfacing operation upon the minor areas be completed first.

It is to be particularly noted that when said glass and abradingelements are relatively rotated, upon said relatively eccentric axes, inaccordance with my method, said axes are maintained relativelystationary throughout the operation. In other words, my method avoidsall ofthe planet-- ary, oscillatory and gyratory movements of the axesof rotation of the glass and abradwhere the mechanism is arranged forpol ishing a surface whichhas been thus generated, for, in the lattercase, the axis 30', of

rotation of the lap 26, remains normal to the surface being polished,regardless of any freedom said lap might have by reason of such looseconnection.

Of course it would be more convenient and expeditious to efi'ect allabrasion of the glass wholly by concentric relative rotation. of theglass and abrading elements, but such abrasion forms circular scratchesor ruts in Y vent the formation of such the abraded surface, due to irrelarities in the forin or distribution of the a rading material, andtherefore, for the finer abrasion, it is preferable to rotate the glassand abrading elements eccentrically to each other, in accordance with mymet 0d, and thus precircular irregularities,-b thus causing continualchange in the relatlon of the abrading and abraded surfaces durin theirrelative rotation.

The glass bfimks land 6 are primarily molded or dropped, as nearly aspossible, throughout their entire area, to the curvature finallyintended for the major area or areas 4, and said minor areas 3 may berough and fine ground by suitable laps of ordinary construction, suchabrasion of course formin a shoulder, such as indicated at 7 in Fig.where the area 3 is'ofiset from the area 4. I prefer to employ for roughand fine grinding the major areas 4, the lap 8 shown in Fig. III havingthe annular convex abrading surface 9 with the central recess 10, saidrecess being coextensive with said minor areas 3 so as to avoid abradingthe latter, while abrading both the major areas 4 by the annular lapsurface 9 or material carried thereby.

Said lap 8, which has the conical socket 12 to frictionally engage theconical mandrel- 13 by which it is rotated, carries means arranged tovariably limit the axial extent of the abrading action of said annularsurface 9 with respect to said blank or blanks, including the screw 15which is adjusted axially in said lap to contact with the templet 16which may be any suitable element having the curvature of the minor area3. For instance, said templet may have a four dioptric curvature andsaid lap surface 9 have a six dioptric curvature. Then I set in therecessed area 3 of thelens blank a gage plate 17 of any thicknesssuflicient to permit said lap 8 to clear said shoulder 7 when said screw15 bears upon said late 17 as shown in Fig. IV; and interpose t e samethickness of gage plate between thecollar 18 v on said mandrel 13 and asuitable stop, conveniently on the frame bearing 20 through which saidmandrel is movable toward and away from the lens. Said collar 18 may beadjustable on said mandrel by the set screw 21, but I prefer to provideadjusting means which may be more accurately set, including the screwstud 23 engaging said bearing 20' and which may be locked in adjustedposition by the nut 24. After such adjustment, the age plates '17 beingremoved both from the ens and from said stud 23, the latter stops thedownward abradin movement of the mandrel 13 precisely w en the lap 8reaches the position with respect to the lens that it occupied withrespect to the templet, thus eliminating any shoulder at the juncan axis30 which extends through the center" of the curvature common to themajor areas 4 of both of said blanks which are conveniently held in theopposite counterpart relation shown in Fi which 'is preferab y rotatedduring the abradingoperation, upon the axis 32 which extends through therespective centers 53 and -54 of the curvatures of all ofsaid areas 3and 4 but coincides with a radius different from said axis of rotation30 of the abrading surface 27. Both of said axes 30 and 32 remainstationary operations aforesaid.

throughout the abrading VII, in the holder 31' I Said holder 31 isconveniently provided with the conical socket 34 to frictionally engagethe conical mandrel 35 from which it may be forcibly removed by rotationof the nut 36 (which engages the screw thread 38 on said mandrel 35)when it is desired to substitute another holder, of different curvature,in connection with said mandrel. In said fine grinding operation saidabrading surface 27 of the lap 26 is uncovered,the

only substance between said abrading surface and the glass surface beingthe. comminuted abradlng material. However, when it is desired to polishwith said lap 26, its surface 27 is covered, conveniently by the silktextile fabric 40 which is held thereon by the, ring 41, and said fabriccarries the polishing material.

The surface to be abraded being rotated with the minor area or areas 3,at the axial region thereof, and the major area or areas 4 at the distalregion thereof; it is to be noted that said circular recess 28 in saidlap 26, being concentric with its axis of rotation 30, 1s presented overthe entire minor area 3, eccentrically to the axis of rotation of saidarea 3, so that the latter is not abraded by said lap 26 while thelatter is employedto abrade the major area or areas 4, in an annulusencircling the axis 32 of rotation of axis.

Said minor area 3 may be conveniently polished by the lap 42; shown inFig. VIII covered-by the textile fabric 43 held thereon by the ring 45.Said lap 42 is also rotated eccentrically to the glass, on an axis whichis eccentric to the axis 32 of rotation of the the glass, but eccentricto that glass, so as to avoid mag circular scratches therein.

'lhe rotary movement of said lensjhlanlx l or blanks 6 may beconveniently edected by providing said mandrel with the hand wheel 46.Said laps 26 and 4L2 may be conveniently rotated by engagement with theband wheel 48 having central and eccentric studs engaging correspondingseats 50 and 51 in said laps. Said hand wheel 48 may be convenientlyjournaled in the hearing 49 which is angularly adjustable on the pivot52 to direct the axes of rotation of said laps 26 and 42 throughdiderent centers of curvature, as 53 and 54.

It may be observed that the axes of said I cccentrically rotary laps 26and 42 are in respectively diderent angular relation with the axis 32 ofrotation of the lens holder 31, and it is to be noted that the relationof said axes may not only he varied anlarly, but that the centers ofoscillation of said axes may be shifted toward or away from the abradingsurface in accordance with the curvature of such surfaw. For instance,the center 53, with respect to which the axis 36 of the lap 26 isadjusted to vary the angular relation of said axis with respect to theaxis of the surface a of the lens blank to be abraded, is also adjustedto coincide with the center of the six dioptric curvature oi" the lattersurface; and the center 54:, with. respect to which the axis of the lap4:2 is adjusted to vary the angular relation or said axis with respectto the axis 32 off the surface 3 of the lens, is also adjusted to coincide. with the center of the four dioptriccurvature of said area 3. Suchadjustments may he efi'ected by any convenient means. For instance, saidhearing 20 may have bolts 55 and 56 fitted in respective slots 58 and 59extending parallel with said axis 32 in a supporting frame 60, andhaving nuts 62 and 63 to secure said bearing in adjusted position. insuch construction and arrangement the bolt 55 serves as a pivot uponwhich the bearing 20 may be angularly adjusted, said bolts 56 beingfitted through slots 57 in said bearing, extending transversely to theslot 69 in said frame, to permit such adjustment.

As shown in Figs. IX and X, the mandrel 13 is provided with the bandwheel 64, ad justably secured thereon by the set screw 65, by which itmay be conveniently rotated. Said mandrel, and the appurtenancesthereof, may be raised and lowered by the handle 66 whlch isconveniently fulcrumed at 67 on said bearing 20, and en aged with thestud 69 on the collar 70 in w ich the hub of said wheel 64 turns. Assaid mandrel 13 tends to gravitate to resent said collar 18 in contactwith the ad ustable screw stud 23, l find it convenient to provide meansby which it may be upheld in idle position, including the strut 71 whichis pivo on said essence it do not dmire to limit myseli to the precisedetails of ootruction and arrangement herein set forth, as it is obviousthat various modifications ma he made therein without departing from t eessential features of my invention as defined in the apded clais,

ll claim 2- l. The method of malning bifocal lenses which consists inrotating the hlto he abraded, with the minorlarea at the axial regionthereof and the jor area at the distal region thereof, while rotatingabrading means contious to said major area in an annulus encircling theaxis of rotation of said blank but eccentric to that axis; andpreventing any change in the direction of the respective axes during theahrading operation; and therehy preventing abrasion of the axial, minorregion of said blank while circularly ahrading an annular major regionof said hla concentric with the axis of rotation of said blank buteccentric to the axis of rotation oi the abrading means,

2. The method oi mahng lenses which consists in rotating the blank to heabraded, while rotating ahrading means contiguous to said hlanlr in anannulus encircling the axis oi rotation of said blank but eccentric tothat axis; and thereby preventing abrasion or the axial region or saiblank while circularly ahrading an annular region of said hlanlrconcentric with the axis of rotation of said hlanlr hut eccentric to theaxis of rota tion of the abrading means; and maintaining the respectiveaxes in unvarying relation with each other during the ahradingoperation.

' 3. The method of making bifocal lenses which. consists in rotatingglass for two lenses with respective minor areas adjoining each otherand between their respective maj or areas; said minor areas having acoon center of curvature upon the axis of rotation of the glass and saidmajor areas having a coon center of curvature upon said axis; circularlyabrading the minor area for both lenses simultaneously, by meansrotating upon an axis coincident with the axis ofrotation oi? the glassand while preventing abrasion of the major area; then circularl ahradingthe major area for both lenses s1- multaneously, by means rotating uponan axis coincident with said axis of rotation oi the glass; thencircularly abrading the major area for both lenses simultaneously, whilepreventing abrasion of the minor area, with the glass and ahradingelement rotating upon axes respectively coinciding with difierent withdififcrent so curvature of sai ill) nseaaee minor area for both lenses;and preventing any change in the direction of said axes dur ing theabrading operation.

4. The method of making a bifocal lens, which consists in recessing aminor area of a lens blank with respect to a major area thereof soas tobe of less thickness at said minor areathan at said major area; andthereafter rotating said blank upon an axis concentric with said minorarea while rotating surfacing means contiguous to said major area in anannulus encircling the axis of rotation of said blank but eccentric tothat axis; and thereby preventing contact of said surfacing means withsaid minor area while surfacing said major area; and preventing anychange in the relative angular position of the respective axes ofrotation during such abrading operation until said major area is reducedto the thiclmess ofsaid minor area.

5. The step in a method of making a bitecal lens, which consists incompleting the surface of the major area thereof before completing thesurface of the minor area thereof; and by rotating the blank to besurfaced,

while rotating surfacing means contiguous to said blank in'an annulusencircling the axis of rotation of said hi buteccentric to that axis;and thereby preventing contact of said surfacing means wlth said mlnorarea while surfacing said major area; and preventing any change in therelative angular position of the respective axes of rotation during suchsurfacing operation.

6. The method of making a bifocal lens, which consists in recessing amajor area of a lens hlank with respect to a minor area thereof so as tobe of less thickness at said major area than at said minor area; androtatin said blank upon an axis concentric with sai minor area whilerotatingsurfacing means contiguous to said major area in an annulusencircling the axis of rotation of said blank but eccentric to thataxis; and thereby preventing contact oi said surfacing means with saidminor area-while surfacing said major area; and preventing an change inthe relative angular position 0 the respective axes of rotation duringsuch abrading o oration. In testimony whereof, I have ereunto signed myname at Philadel hia, Pennsylvania, this seventeenth day of arch, 1914.HENRY A. SCHEUERLE. Witnesses:

Anrnnn E. Peron, Anna lsnvrrz.

